Chair for Extended Seating Periods

ABSTRACT

In order to provide comfort during prolonged seating periods and facilitate proper sitting posture, a chair is configured to include a central chair portion defining a pair of seat back mounting sections, a pair of front leg mounting sections, a pair of rear leg mounting sections, and a seat surface. A seat back including a pair of seat back extensions is provided, with each of the seat back extensions mountable on one of the seat back mounting sections. A pair of front leg extensions is mountable on the front leg mounting sections of the central chair portion, while a pair of rear leg extensions is mountable on the rear leg mounting sections of the central chair portion. Such a chair construction permits the seat back, the front leg extensions, and the rear leg extensions all to be adjustable relative to the seat surface and lockable in any of a plurality of discrete positions with respect to the seat surface.

The present application claims the priorities of U.S. Provisionalapplication Ser. No. 60/786,049, filed Mar. 27, 2006, and U.S.Provisional application Ser. No. 60/872,591, filed Dec. 4, 2006, thedisclosures of which are incorporated herein by reference in theirentireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the configuration of a chair,occasionally referred to as an ALCAT chair in the following description,that facilitates good, relaxed posture and, at the same time, providesadequate upper back support when a user is properly seated, as well ascertain methods of using such a chair to provide greater comfort duringprolonged sitting sessions. The invention is ideal for musicians orother individuals who find it necessary or desirable to remain seatedfor extended time periods.

2. Description of Related Art

Chairs in common use today have a number of basic problems. Typicallysuch a chair includes a solid, full back rest defining, together with aseat surface, a minimal opening at the base of the back rest. Variousattempts have been made to improve chair comfort, such as the provisionof ergonomic curves providing lumbar and overall back support and curvedor scooped out seat surfaces. The user of a chair having such features,however, still typically must exert significant physical effort to sitwith good, relaxed, comfortable posture, which is essential if that useris to remain seated for an extended time period. A conventional chairconstruction tends to force a user to sit on gluteal muscles, impose abackward curve to the spine, and produce a caved-in chest, affectingheart and lung efficiency. Shoulder tension may also affect the arms andhands of a user while seated on a conventionally configured chair, and arounded lumbar and/or sacral area tends to produces muscle stress andpotentially creates possible danger to vertebrae due to possibleherniation or exacerbation of other existing conditions.

A conventional chair construction is shown in FIG. 16. When viewedlaterally, with “good” sitting posture, a plumb line P perpendicular tothe floor F should be aligned with the user's ear, shoulder, hip joint,and ischium, and a line L parallel to the floor at the level of theuser's hip joint is preferably slightly higher than the user's kneejoint. The user of a conventional chair construction such as that shownin FIG. 16 could have significant difficulty is achieving or maintainingthis “good” sitting posture, i.e. a posture considered to provide themost relaxed sitting position, in which the pull of gravity on theuser's body and associated stresses produced due to misalignment areminimized. As it is difficult for the user to keep his or her torso inan essentially upright or perpendicular position relative to the seatsurface, a relatively large body area is subjected to the force ofgravity. If a chair such as that shown in FIG. 16 has a scooped orrounded seat surface and a minimally open space between the backrest andthe seat surface, such problems could be amplified.

SUMMARY OF THE INVENTION

It is one object of the invention to provide a chair configuration thatboth facilitates good, relaxed posture and provides adequate upper backsupport when a user is properly seated.

Another object of the invention is to use such a chair configuration toproduce greater comfort during prolonged sitting sessions, thusrendering it ideal for musicians or other individuals who find itnecessary or desirable to remain seated for extended time periods

These objects, as well as other objects and various features andadvantages that will become apparent, are achieved by way of a chairaccording to the invention that is particularly adapted to providecomfort during prolonged seating periods and to facilitate propersitting posture. Such a chair, according to the invention, includes acentral chair portion defining a pair of seat back mounting sections, apair of front leg mounting sections, a pair of rear leg mountingsections, and a seat surface. A seat back including a pair of seat backextensions is provided, with each of the seat back extensions mountableon one of the seat back mounting sections. A pair of front legextensions are mountable on the front leg mounting sections of thecentral chair portion, while a pair of rear leg extensions are mountableon the rear leg mounting sections of the central chair portion. The seatback, the front leg extensions, and the rear leg extensions are alladjustable relative to the seat surface and lockable in any of aplurality of discrete positions with respect to the seat surface toproduce the improved comfort during prolonged sitting sessions as notedabove.

The central chair portion may be either collapsible or substantiallyrigid and non-collapsible. Manually releasable latches, biased intolocking engagement, may be disposed on the central chair portion toreleasably secure the seat back, the front leg extensions, and the rearleg extensions in position relative to the seat surface. The front legextensions, the rear leg extensions, or both the front leg extensionsand the rear leg extensions can be substantially rigidly connected toeach other by a support strut, if desired. It is also possible toinclude an arm rest assembly having an arm rest surface that is alsolockable in a plurality of discreet positions relative to the seatsurface. Rollers or casters could be disposed at ends of the front andrear leg extensions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view from above of a first ALCAT chairembodiment.

FIG. 2 is an exploded posterior view showing a first support frame, anadjustable seat back, and adjustable leg extensions of the chair shownin FIG. 1.

FIG. 3 is an enlarged, part sectional view of a locking device formed bya manually releasable latch.

FIG. 4 is a front view of the elements illustrated in FIG. 2 in anassembled condition.

FIG. 5 is a top view of the seat or seat surface of the chair as well asof the supporting frame for the seat.

FIG. 6 is a side view of the seat shown in FIG. 5.

FIG. 7 is an enlarged view of one of a pair of hinge links partiallyinterconnecting the support frames and seat of the first chairembodiment together.

FIG. 8 is a view illustrating a second support frame and adjustable legextensions of the chair shown in FIG. 1.

FIG. 9 shows a second embodiment of a chair according to the inventionthat includes rollers or casters mounted on lower ends of the legextensions.

FIGS. 10 and 11 show an adjustable arm rest assembly.

FIGS. 12 and 13 illustrate yet another embodiment of the chair in whichthe central portion of the chair is substantially rigid andnon-collapsible.

FIG. 14 shows the user of a chair according to the invention in onepreferred sitting position.

FIG. 15 shows the user of a chair according to the invention in anotherpreferred sitting position.

Figure illustrates a user sitting on a conventionally constructed chair.

DETAILED DESCRIPTION OF THE INVENTION

The manner in which a first support frame 30, a second support frame 40,and a seat 50 cooperate to define a collapsible central portion of afirst ALCAT chair embodiment is apparent from FIG. 1. The first supportframe 30 is configured as a substantially rigid, approximately “H”shaped structure having substantially parallel side legs 32interconnected by a laterally extending strut 34. The side legs 32 andthe strut 34 could be made of any material appropriate for constructionof collapsible chairs, such as wood, aluminum, steel, or plastic havingsufficient strength and stiffness. In one configuration, the legs 32 andthe strut 34 are constructed of ⅞″ steel tubing, with the strut 34 spotwelded at its ends to the legs 32 at appropriate locations 36.

The second support frame 40 is also configured as a substantially rigid,approximately “H” shaped structure. The second support frame hassubstantially parallel side legs 42 interconnected by a laterallyextending strut 44. Again, the side legs 42 and the strut 44 could bemade of any material appropriate for construction of collapsible chairs.In one configuration, the legs 42 are constructed of ⅞″ steel tubing andthe strut 44 is constructed of ⅝″ steel tubing, with the strut 44 spotwelded at its ends to the legs 42 at appropriate locations 46 (indicatedin FIG. 8).

The seat 50 is defined by a substantially rigid seat frame 52. Asillustrated in FIGS. 1, 5, and 6, the frame 52 has a square orrectangular perimeter, but it is to be noted that the perimeter of theframe 52 could be circular or oval or could have any other appropriateconfiguration. The seat surface 54 could either be constructedintegrally together with the frame 52 as a single piece of material or,as shown in FIG. 1, defined by a separate, possibly removable,upholstered cushion or fabric surface, configured as desiredaesthetically. It is imperative, however, that the seat be relativelyflat and firm.

A pair of hinge links 60 cooperates with the seat frame 52 tointerconnect the first support frame 30, the second support frame 40,and the seat frame 52 together to produce the collapsible central ALCATchair portion. Holes 64, best shown in FIG. 7, are drilled or otherwisedefined at forward and rearward ends of the hinge links 60. The sidelegs 32 of the first support frame 30 are provided with holes 38 adaptedto align with respective holes 64 at forward ends of the hinge links 60,while the legs 42 of the second support frame have holes 48 adapted toalign with respective holes 64 at rearward hinge link ends. Bolts,rivets, or other such elements 62 extend through each aligned pair ofholes 38, 64 and 48, 64 to pivotally secure each of the side legs 32 and42 to respective ends of the hinge links 60.

Each of the first support frame side legs 32 is also provided with ahole 39 provided at a location below the location of the hole 38, whileeach of the second support frame legs 42 is also provided with a hole 49provided at a location below the location of the hole 48. A bolt, rivet,or other such element 66 extends through each of the holes 39 in thefirst support frame 30 and an aligned hole 53 in the seat frame 52 topivotally secure each of the side legs 32 to the seat frame 52. Anotherbolt, rivet, or other such element 66 also extends through each of theholes 49 in the second support frame 40 and an aligned hole 55 in theseat frame 52 to pivotally secure each of the side legs 42 to the seatframe. Connecting a first support frame leg 32, a second support frameleg 42, one of the hinge links 60, and a side of the seat frame 52together in this way produces a roughly trapezoidal lateral link 70 asshown in FIG. 1. Upper ends of the second support frame side legs 42 maybe provided with resilient rubber or plastic caps or bumpers 43.Abutment between outside surfaces of the side legs 32 and either theupper ends of the second support frame side legs 42 or the bumpers 43,if they are provided, serves, together with the lateral links 70, tostabilize the central ALCAT chair portion when the overall chair is inits expanded, in-use, open position.

A seat back 72 is mountable on the side legs 32 of the first supportframe so as to be displaceable along the side leg longitudinal axes. Inthe configuration shown in FIGS. 1 and 2, the seat back 72 includes anapproximately “U” shaped seat back frame 74 having a web 76 (FIG. 2)interconnecting the base 78 and legs 80 of the frame 74. For reasonsthat will become clear, the legs 80 can properly be referred to as seatback extensions. In one configuration, the base and legs could be formedof a unitary bent piece of 1″ steel tubing and the web could be a steelsheet of appropriate thickness welded to the tubing. For comfort andpleasing aesthetics, fabric or a separate, possibly removable cushion 82could be constructed integrally with or attached removably to the seatback 72. As illustrated in FIGS. 1 and 2, the cushion 82 is attachedremovably to the web 76 by fasteners 84, such as screws.

To provide for locking the seat back 72 in a plurality of discretepositions along the side leg longitudinal axes, each leg 80 of the seatback frame 74 is provided with a longitudinally extending series ofopenings 86. In the configuration shown, the openings 86 are provided inwalls of tubing forming the seat back frame 74. Each of the openings 86is configured to cooperate with a spring button mechanism 90, which isprovided near an upper end 100 of each first support frame leg 32 anddefines a manually releasable latch. The spring button mechanism, bestshown in FIG. 3, serves to lock the seat back frame legs 80 and thefirst support frame side legs 32 in position relative to each other.Each spring button mechanism includes an approximately cylindricalbutton or cap 92 welded or otherwise secured to or provided with abiasing element 94, such as a leaf or coil spring. In the configurationillustrated in FIG. 3, the biasing element 94 has a base 96 secured inany convenient manner to a wall of one of the first support frame legs32. The button or cap 92 of each mechanism protrudes through an opening98 in the support frame side leg 32 approximately diametrically opposedto the base 96.

To lock the seat back 72 in a discrete position relative to the firstsupport frame side legs 32, the upper ends 100 of the first supportframe side legs 32 are inserted into the larger diameter lower ends ofthe seat back frame legs 80. The tops of the legs 32 thus form a pair ofseat back mounting sections. The buttons or caps 92 are biased underaction of the biasing elements 94 through aligned openings 98 and 86 toproduce releasable locking engagement between the seat back 72 and thefirst support frame 30. By pressing the buttons or caps 92 inwardly intoopenings 86 against forces applied by the elements 94, a user candisable locking engagement between the buttons or caps and the holes andadjust the overall position of the seat back 72 relative to the supportframe 30. Once a desired relative position between the seat back 72 andthe support frame 30 is reached, the buttons or caps 92 can be permittedby a user to remain engaged within the appropriate set of openings 86 tolock the seat back 72 in the desired position. Conventional locking nuts102 may also be included at the lower ends of the seat back frame legs80 to provide added or redundant frictional locking between the firstsupport frame legs 32 and the seat back frame legs 80. The seat back 72can be removed from engagement with the first support frame legs 32 byreleasing the locking nuts 102, again pressing the buttons or caps 92inwardly into openings 86 against forces applied by the elements 94 todisable locking engagement between the buttons or caps and the holes,and withdrawing the first support frame legs 32 from the lower ends ofthe seat back frame legs 80.

Each of the first support frame legs 32 also has a lower end 101 that isreceivable in a respective leg or leg extension 104, which, asillustrated, is formed by a tube, constituting part of a first supportleg extension frame 106. The lower ends of the legs 32 thus form a pairof front leg mounting sections for legs or leg extensions 104. The legextension frame 106 includes a pair of the leg extensions 104interconnected by a laterally extending support strut 108 and, as shown,is configured so as to have a substantially rigid, approximately “H”shaped structure. The leg extension frame 106 could be made of anymaterial appropriate for construction of collapsible chairs, such asaluminum, steel, plastic having sufficient strength and stiffness, oreven wood. As illustrated, the frame 106 is constructed of steel, withthe support strut 108 spot welded at its ends to the leg extensions 104at appropriate locations 110. Each of the leg extensions 104 is providedwith a longitudinally extending series of openings 112 configuredsimilarly to the openings 86 in the seat back frame. Each series ofopenings 112 respectively cooperates with another spring buttonmechanism 90, configured essentially the same as the spring buttonmechanism described above, located adjacent a lower end 101 of a supportframe leg 32. The spring button mechanisms 90 and the openings 112together provide for locking the first support leg extension frame 106in and releasing the first support leg extension frame from discretepositions along the side leg longitudinal axes. Conventional lockingnuts 102 may again be included around the upper ends of the legextensions 104 to provide added or redundant frictional locking betweenthe first support frame legs 32 and the leg extensions 104 of the firstsupport leg extension frame 106. Rubber or plastic caps 114 can beprovided at lower ends of the leg extensions 104 to avoid undue wear onfloors or other support surfaces. FIG. 4 shows the first support frame30, the seat back 72, and the first support leg extension frame 106 inan assembled condition.

Each of the second support frame side legs 42 has a lower end that isreceivable in a respective leg or leg extension 120, which, asillustrated, is formed by a tube, constituting part of a second supportleg extension frame 122. The lower ends of the legs 42 thus form a pairof rear leg mounting sections. The leg extension frame 122 includes apair of the leg extensions 120 interconnected by a laterally extendingsupport strut 124 and is configured essentially identically to the firstsupport leg extension frame 106. Each of the leg extensions 120 isprovided with a longitudinally extending series of openings 126, againconfigured similarly to the openings 86 in the seat back frame 74. Eachseries of openings 126 respectively cooperates with yet another springbutton mechanism 90, configured essentially the same as the springbutton mechanism described above, located adjacent the lower end of eachof the second support frame side legs 42. FIG. 8 illustrates the buttonsor caps 92 of such spring button mechanisms received in openings 126 tolock the second support leg extension frame 122 in a discrete positionwith respect to the second support frame 40. As with the first supportleg extension frame 106, the spring button mechanisms and the openings126 together provide for locking the second support leg extension frame122 in and releasing that second support leg extension frame fromdiscrete positions along the side leg longitudinal axes. Conventionallocking nuts 102 may once again be included, this time at the upper endsof the leg extensions 120 to provide the added or redundant frictionallocking noted previously, and rubber or plastic caps 114 can be providedat lower ends of the leg extensions 120.

Exemplary dimensions and compositions of certain parts of the ALCATchair are mentioned above. Some of these dimensions and compositionswill now be reiterated in the following overall discussion, which is setforth simply in order to provide an illustration of the size of oneembodiment of the invention and is not to be considered limiting in anyway. As noted above, the side legs 32 and the strut 34 can be formed of⅞″ outer diameter spot welded steel tubing. Centers of holes 38 and 39in each leg 32 can be separated by 2 inches, and centers of holes 38 canbe separated from openings 98 by 9 inches. The center of each hole 39can be separated from the longitudinal centerline of the strut 34 by 6″,and from the respective lower end 101 by 17″. The strut 34 may have alength of 16.25″.

Many dimensions of the frames 106 and 122 are essentially the same. Thesupport struts 108, 124 may be formed of ⅞″ outer diameter tubing, canhave a length of 16.125″, and may have centerlines displaced 3″ from thelocation of the locking nut 102 disposed at the upper end of legextensions 104, 120. The leg extensions 104, 120 may be formed of 1″tubing. Openings 86, 112, and 126 in each respective series of openingsmay be spaced 1″ apart, and each series shown in the drawing figuresincludes five openings.

The U-shaped seat back frame 74 may be constructed of 1″ outer diametertubing, and the lateral fasteners 84 (FIG. 2) may be disposedapproximately 10″ vertically from the underside of the locking nuts 102disposed on ends of the legs 80.

The seat frame 52 may be 16″×16″, 0.125″ thick, and 1.50″-1.75″ deep.The hole 53 may have its center displaced 9″ from the front edge of theframe 52, while the hole 55 may have its center displaced 1.50″-1.75″from the rear edge of the frame 52.

Finally, the hinge link 60 may be 4.5″ in length, the strut 49 may be16.25″ in length, each hole 48 may be separated by 1.25″ from the tip ofa cap or bumper 43 and by 5.5″ form a centerline of the strut 44. Eachleg 42 may have an overall length of 19.75″.

The second ALCAT chair embodiment illustrated in FIG. 9 is essentiallythe same as the first embodiment, except that rollers or casters 130 areprovided at lower ends of the leg extensions 104 in place of the caps114 included in the first embodiment. The rollers or casters 130 providethe chair with improved mobility. The rollers may be approximately 2″ indiameter, although this dimension is not critical and could besignificantly larger or smaller.

FIGS. 10 and 11 show a version of the second ALCAT chair embodimenthaving an adjustable arm rest assembly 132 mounted on one side 134 ofthe seat frame 52. The arm rest assembly 132, of course, could beutilized in conjunction with the first ALCAT chair embodiment describedabove. An additional adjustable arm rest assembly could also be mountedon the other side of the seat frame if support for both arms of theALCAT chair user is desired.

The arm rest assembly includes a base 136 connectable to the seat frame52, for example by fasteners, such as bolts, screws, or rivets, passingthrough holes 138. The base 136 may be a pressed metal sheet or solidmetal, possibly plastic or another material, and includes an opening 139in one of its walls through which a spring biased button 140 extends.The button 140 is dimensioned to protrude through any of a series ofopenings 142 provided in a stem 144 to which an arm rest 146 is mountedor with which the arm rest is integrally formed. A pad or cushion 148may be provided on the arm rest 146 for comfort. The stem 144, in theconfiguration illustrated, defines a sleeve which fits over the base 136for vertical movement. The arm rest 146 is lockable in any of a numberof discrete vertical positions relative to the seat surface 54 by springbiased movement of the button 140 into an appropriate aligned opening142. Another ergonomically adjustable feature is thus provided by thearm rest assembly or assemblies.

Exemplary dimensions of the arm rest assembly components are nowprovided solely to provide an illustration of the size of that assembly.These exemplary dimensions are not to be considered limiting in any way.The base 136 may be 8.5″ in height, 3″ wide at its base, and 2.5″ wideat its upper end. The stem 144 may be 2.75″ in width, and the series ofopenings 142 may provide for 8″ of adjustability. The pad or cushion mayhave a 1″ thickness and a 8″ length.

FIGS. 12 and 13 show an ALCAT chair configuration with a substantiallyrigid, non-collapsible central portion 160. In this configuration, theseat back 72 is identical to the seat back 72 described in connectionwith the first ALCAT embodiment. Leg extensions 154 of thisconfiguration, however, differ from the leg extensions 104 and 120 ofthe first ALCAT embodiment in that the extensions 154 of the presentconfiguration are independent of one another and are not interconnectedby support struts. In all other respects, the extensions 154 areconfigured identically to the leg extensions 106 and 120 describepreviously.

The non-collapsible central portion 160 of the configuration illustratedin FIGS. 12 and 13 includes a rear support frame 162 and a front supportframe 164. Each of the front and rear support frames 162, 164 may beconstructed of tubing similar to that of the first support frame 30 orthe second support frame 40 of the first ALCAT chair configuration. Therear support frame 162 is composed of a pair of parallel frame elements,each including sections 163 a and 163 b, and a rear cross strut 170.Each frame element is bent slightly in an approximately central portionthereof so that central axes of the sections 163 a and 163 b define anobtuse angle α relative to one another.

The front support frame 164 includes a pair of parallel frame elements,each including sections 165 a and 165 b. In this embodiment, therefore,the tops of sections 163 a define a pair of seat back mounting sections,the bottoms of leg sections 163 b define a pair of rear leg mountingsections, and the bottoms of leg sections 165 b define a pair of frontleg mounting sections. The seat section 165 a of each frame element isjoined by a weld 166 to one of the rear frame elements at an apexdefined by the junction of the sections 163 a and 163 b. The welds 166also serve to connect the rear cross strut 170 between the apices of therear frame elements. The front support frame 164 also includes a frontcross strut 172. Each of the front support frame elements is bentsignificantly in an approximately central portion thereof so thatcentral axes of the sections 165 a and 165 b define a small obtuse angleμ (less than approximately 120°) relative to one another, thuseliminating any need to weld the sections 165 a and 165 b together. Eachseat section 165 a of the front support frame 164 is joined by anotherweld 166 to one end of a front cross strut 172, while each leg section165 b receives one of the extensions 154 as shown. A seat 180, defininga seat surface, is removably mounted on the seat sections 165 a and/orthe cross struts 170, 172 as illustrated.

FIG. 14 illustrates a “base” position of a user that allows freedom ofmovement and natural return to a “base” or “norm,” and is considered themost relaxed sitting position. The base position shown in FIG. 14minimizes the pull of gravity on the body and associated stressesproduced due to misalignment. This is due to the essentially upright orperpendicular position of the user's torso relative to the seat surface,which minimizes the body area subjected to the force of gravity. Theuser's position shown in FIG. 14 is suitable for times in which theischia (sit bones) of the user are located at or near the edge of theseat surface. When viewed laterally, with “good” sitting posture, aplumb line P perpendicular to the floor F is aligned with the user'sear, shoulder, hip joint, and ischium. In the preferred, mostcomfortable sitting position, a line L parallel to the floor at thelevel of the user's hip joint is slightly higher than the user's kneejoint. Many professionals who spend a great deal of time sitting, suchas musicians, prefer the position shown in FIG. 14, as that positionallows the entire pelvic area to be aligned in a manner similar to thealignment provided by way of proper standing posture. As the knees ofthe user are lifted, muscles in the lumbar sacral area are put intension.

The position illustrated in FIG. 15 is similar to that illustrated inFIG. 14, but with buttocks of the user positioned so as to protrudepartially through an open space surrounded, for example, by the cushion82, the seat surface 54, and the side legs 32 of the first ALCAT chairconfiguration. The open space should be sufficiently wide and tall topermit the buttocks to readily protrude as illustrated As FIG. 15 shows,the plumb line P can be maintained with provision of an open spacehaving adequate area. The adjustable leg extension frames or legextensions and the adjustable back rest of the ALCAT chair allowvertical adjustment of portions of the seat surface so that the knee ofa user is at or below the level of the hip joint. Each individual user,of course, could modify the positions of the back rest cushion andeither the adjustable leg extension frames (FIGS. 1-2, 4, and 8-10) orany of the individual legs (FIGS. 12-13) for optimal comfort. The ALCATchair configuration thus facilitates good, relaxed posture and, at thesame time, provides adequate upper back support when a user is in aproper sitting position so as to produce greater comfort for prolongedsitting sessions, thus rendering it ideal for musicians or otherindividuals who find it necessary or desirable to remain seated orextended time periods.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications to thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons of ordinary skill in the art, theinvention should be construed to include everything within the scope ofthe appended claims and equivalents thereof.

1. A chair adapted to provide comfort during prolonged seating periodsand facilitating proper sitting posture comprising: a central chairportion defining a pair of seat back mounting sections, a pair of frontleg mounting sections, a pair of rear leg mounting sections, and a seatsurface; a seat back including a pair of seat back extensions, each ofthe seat back extensions mountable on one of the seat back mountingsections; a pair of front leg extensions mountable on the front legmounting sections of the central chair portion; and a pair of rear legextensions mountable on the rear leg mounting sections of the centralchair portion; wherein the seat back, the front leg extensions, and therear leg extensions are all adjustable relative to the seat surface andlockable in any of a plurality of discrete positions with respect to theseat surface.
 2. The chair of claim 1, wherein the central chair portionis collapsible.
 3. The chair of claim 1, further comprising manuallyoperable locking devices adapted to releasably secure the seat back, thefront leg extensions, and the rear leg extensions in position relativeto the seat surface.
 4. The chair of claim 3, wherein at least one ofthe locking devices is formed by a manually releasable latch, disposedon the central chair portion, that is biased into locking engagement. 5.The chair of claim 2, wherein the pair of front leg extensions aresubstantially rigidly connected to each other.
 6. The chair of claim 5,wherein the front leg extensions are interconnected by a support strut.7. The chair of claim 2, wherein the pair of rear leg extensions aresubstantially rigidly connected to each other.
 8. The chair of claim 7,wherein the rear leg extensions are interconnected by a support strut.9. The chair of claim 1, further comprising at least one arm restassembly having an arm rest surface also lockable in a plurality ofdiscreet positions relative to the seat surface.
 10. The chair of claim9, further comprising a manually operable locking device adapted toreleasably secure the arm rest surface in position relative to the seatsurface.
 11. The chair of claim 10, wherein the locking device is formedby a manually releasable latch, disposed on the central chair portion,that is biased into locking engagement.
 12. The chair of claim 11,wherein the locking device includes a base affixed to a side of a seatframe supporting the seat surface.
 13. The chair of claim 1, wherein thecentral chair portion is substantially rigid and non-collapsible. 14.The chair of claim 1, further comprising rollers or casters disposed atends of the front and rear leg extensions.
 15. The chair of claim 5,wherein the pair of rear leg extensions are also substantially rigidlyconnected to each other.
 16. A process facilitating proper seating toprovide comfort during extended periods of sitting comprising: providinga central chair portion including a pair of seat back mounting sections,a pair of front leg mounting sections, a pair of rear leg mountingsections, and a seat surface; mounting a seat back including a pair ofseat back extensions on the seat back mounting sections such that eachof the seat back extensions is received on one of the seat back mountingsections; mounting a pair of front leg extensions on the front legmounting sections of the central chair portion; mounting a pair of rearleg extensions on the rear leg mounting sections of the central chairportion; and adjusting at least one of the seat back, the front legextensions, and the rear leg extensions relative to the seat surface andlocking it in any of a plurality of discrete positions with respect tothe seat surface.
 17. The process of claim 16, wherein the central chairportion is collapsible.
 18. The process of claim 16, wherein the atleast one of the seat back, the front leg extensions, and the rear legextensions is releasable from the discrete positions by operating amanually operable locking device.
 19. The process of claim 18, whereinat least one of the locking devices is formed by a manually releasablelatch, disposed on the central chair portion, that is biased intolocking engagement.
 20. The process of claim 16, wherein the centralchair portion is substantially rigid and non-collapsible.